1. Field of the Invention
The invention relates to a multi-chip module (MCM) packaging device, especially to an MCM using the flip-chip bonding technology.
2. Description of the Related Art
Because of the increasing requirements for the portability and integral versatility of consumer electronic products, the packaging technology for the multi-chip module undoubtedly can provide the best way to meet above-mentioned requirements. However, in order to integrate functions of multiple chips, the technique mostly needs to use multi-layer circuit laminated board. For example, as shown in FIG. 1, it shows a substrate 10 provided with six-layer circuit layers.
The price of the substrate is 40˜60% of the total packaging cost, and the manufacturing cost of the substrate depends on the number of the circuit layers. For example, the substrate with two-layer circuit layers used for 256 Input/output (I/O) ball grid array package has the unit price of USD 0.5˜0.8. Under the same requirements, if the package is accomplished by the substrate with four-layer circuit layers, the unit price thereof is USD 1.6˜4.0. Accordingly, the reduction in the number of the circuit layers may greatly cut down the direct material cost in manufacturing.
FIG. 2 is a schematic cross-sectional diagram of a conventional multi-chip module packaging device 20, which uses flip-chip method to mount the first chip 21 and the second chip 22 on the substrate 23, respectively. The electrical signal will be transmitted between the two chips, and it is through the metal layers of the substrate 23, the bump 24 of the first chip 21 and the bump 25 of the second chip 22 to complete the complex transmissions. The substrate 23 can serve as the signal transmission path between the chips, and it has another important function of serving as the signal transmission path between the chip and the external system (e.g. the mother board of a computer, figure not shown), which is achieved by the solder balls 26 under the substrate 23. If it is desired that more circuit traces may be contained on the limited layout area of the substrate 23, a substrate with more circuit layers needs to be designed, and the circuit routing through the added circuit layers must be completed. If it is desired to have more functions or I/Os in the same packaging area of an electrical device, the number of circuit layers for the substrate must be relatively increased, and thus the problem of increased production cost is accompanied.